Apparatus for scanning sheet-shaped recording medium

ABSTRACT

An apparatus for scanning a sheet-shaped recording medium comprises a conveyance system provided with a conveying roller and a plurality of nip rollers for conveying the recording medium in co-operation with the conveying roller, and a scanning optical system for scanning the conveyed recording medium by a light beam in a scanning direction normal to the conveyance direction. One of the conveying roller and the nip rollers is fabricated as edge rollers contacting the other of said conveying roller and said nip rollers only near both end portions of the other. The scanning optical system is positioned on the side of the edge rollers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an apparatus for scanning a sheet-shapedrecording medium by a light beam and recording an image thereon orreading out an image therefrom. This invention particularly relates toan apparatus for scanning a sheet-shaped recording medium, which isprovided with an improved sub-scanning conveyance system whereinsub-scanning is conducted by moving the recording medium in onedirection at a predetermined speed during two-dimensional scanning ofthe recording medium by a light beam.

2. Description of the Prior Art

An image scanning method for recording an image on a recording medium orfor reading out an image therefrom by two-dimensionally scanning therecording medium by a light beam is widely used in facsimile devices andthe like. In the method, two-dimensional scanning is conducted bydeflecting a light beam by a light deflector in one direction (mainscanning direction) to form a scanning line on the recording medium andby mechanically moving the recording medium in a direction (sub-scanningdirection) normal to the main scanning direction, thereby forming manyscanning lines in parallel with each other.

As disclosed, for example, in U.S. Patent No. 4,258,264 and JapaneseUnexamined patent Publication No. 56(1981)-11395, the aforesaid imagescanning method is also employed for reading out a radiation imagestored in a stimulable phosphor sheet or for reproducing the read-outradiation image in a recording medium in a radiation image recording andreproducing system. In the radiation image recording and reproducingsystem, it is necessary to regularly conduct scanning in the mainscanning direction at a predetermined period and to carry out movementof the recording medium in the sub-scanning direction at a predeterminedspeed. That is, when the recording medium is moved at a low speed in thesub-scanning direction and, at the same time, a light beam is deflectedin the main scanning direction normal to the sub-scanning direction onthe recording medium, the recording medium must be precisely moved atthe predetermined speed. Otherwise, recording nonuniformity or read-outnonuniformity arises, and it becomes impossible to obtain a reproducedimage accurately representing the image density. Therefore, highaccuracy is required for scanning in the sub-scanning direction,necessitating a high-precision expensive holding means and movementmechanism for the recording medium.

In order to move the recording medium as described above, variousmechanisms have heretofore been used. For example, in one arrangementthe sheet-shaped recording medium is closely contacted with the surfaceof a drum by using the clamping devices or pinch rolls, and the drum isrotated. Or, a suction box is positioned at a part inside of a drum, andthe drum is rotated with the recording medium closely contacted with apart of the drum by suction. In another mechanism, a suction box ispositioned inside of a perforated belt, and the belt is moved with therecording medium placed thereon. In these mechanisms, since the clampingdevices or the suction box is required for closely contacting therecording medium with the drum or the belt, the mechanism becomescomplicated and the apparatus becomes large and expensive.

Further, in the case where a suction box is used, there arise variousproblems in practical use such as noise and vibration from a blower forsuction, fluctuation of the suction pressure, and the like. Particularlyin a scanning apparatus for image recording or read-out wherein therecording medium must be moved precisely and a precise scanning opticalsystem is incorporated, vibration and fluctuation of the suctionpressure cause the movement speed of the recording medium to fluctuateand adversely affect the recording or read-out operation.

In an image read-out scanning apparatus for scanning a recording mediumcarrying an image stored therein by a light beam and for detecting lightcarrying the image obtained thereby, a light guide member is generallypositioned near the recording medium. In this case, in order to improvethe light guiding efficiency, it is generally desired that the lightguide member be positioned as close to the recording medium as possible.However, when the conventional clamping devices or pinch rolls are used,it is not always possible to position the light guide member close tothe recording medium because of the presence of mechanisms protruding inthe vicinity of the clamping devices or the pinch rolls.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide an apparatusfor scanning a sheet-shaped recording medium, which is comparativelysmall and has a simple configuration.

Another object of the present invention is to provide an apparatus forscanning a sheet-shaped recording medium, which securely holds arecording medium and realizes precise optical scanning.

The present invention provides an apparatus for scanning a sheet-shapedrecording medium, the apparatus comprising:

(i) a conveyance means comprising a conveying roller and a plurality ofnip rollers for forming nips for conveying said sheet-shaped recordingmedium in co-operation with said conveying roller by contacting thesurface of said conveying roller, and

(ii) a scanning optical system for scanning said sheet-shaped recordingmedium, which is conveyed by said conveyance means, by a light beam in ascanning direction approximately normal to the conveyance direction ofsaid sheet-shaped recording medium,

(iii) one of said conveying roller and said nip rollers being fabricatedas edge rollers contacting the other of said conveying roller and saidnip rollers only near both end portions of the other,

(iv) said scanning optical system being positioned on the side of saidedge rollers.

The sheet-shaped recording medium may be any photosensitive material onwhich an image can be optically recorded by scanning with a light beamor any image storage medium which carries an image stored therein andwhich releases light carrying the image when scanned by a light beam.The photosensitive material may, for example, be printing paper or aphotographic film. The image storage medium may, for example, be paperor a film sheet carrying an image stored therein, or a stimulablephosphor sheet carrying a radiation image stored therein as disclosed,for example, in U.S. Pat. Nos. 4,236,078 and 4,239,968.

The image storage medium releasing the light carrying the stored imagewhen scanned by a light beam may be of the type releasing light havingthe same wavelength as that of the light beam, i.e. of the typereflecting the light beam, or may be of the type emitting light having awavelength different from that of the light beam.

By the term "edge rollers" are meant rollers contacting the other rolleror rollers, that form nips in cooperation with the edge rollers, onlynear the end portions of the other roller or rollers in the widthdirection thereof. The conveying roller or the nip rollers arefabricated as a pair or edge rollers or two or more pairs of edgerollers. In this case, the widths of a plurality of nip rollers are madeapproximately equal to the width of the sheet-shaped recording medium,and the conveying roller is fabricated as a pair of narrow rollerscontacting only near both end portions of each nip roller.Alternatively, the width of the conveying roller is made approximatelyequal to the width of the sheet-shaped recording medium, and at leastone of a plurality of nip rollers is fabricated as a pair of narrowrollers contacting only near both end portions of the conveying roller.

In the present invention, the nip rollers contact the surface of theconveying roller so that the sheet-shaped recording medium can begrasped therebetween and conveyed. Thus the term "contacting" of the niprollers with the surface of the conveying roller embraces the case wherethe surfaces of the nip rollers directly contact the surface of theconveying roller and the case where the surfaces of the nip rollers andthe surface of the conveying roller are positioned in spaced relation toeach other.

The diameter of the conveying roller may be larger or smaller than thoseof the nip rollers. However, in order to make the apparatus small and toconvey the sheet-shaped recording medium more consistently, the diameterof the conveying roller should perferably be larger than those of thenip rollers.

In the apparatus for scanning a sheet-shaped recording medium inaccordance with the present invention, when the sheet-shaped recordingmedium is scanned by a light beam for image read-out or recording, nipsare formed between the conveying roller and a plurality of nip rollers,and the sheet-shaped recording medium is conveyed therebetween. That is,the sheet-shaped recording medium is conveyed in close contact with theconveying roller while the recording medium is maintained in apredetermined form bent by the roller. Therefore, it is possible toconvey the sheet-shaped recording medium consistently and accurately inthe sub-scanning direction. Also, even if the surface of the recordingmedium is uneven due to curling, distortion or the like when it is leftin the free condition, it becomes even and straight in the widthdirection when it is conveyed in close contact with the surface of theconveying roller, and the even, straight sheet surface is scanned by thelight beam in the main scanning direction. Accordingly, it becomespossible to accurately record or read out an image.

Further, in the apparatus for scanning a sheet-shaped recording mediumin accordance with the present invention, since clamping devices or asuction box is not used, the configuration of the apparatus becomessimple, and the apparatus becomes small, inexpensive and easy tomaintain. Also, the problems of noise and vibration are eliminated.

When the scanning apparatus of the present invention is used for imageread-out, since one of the conveying roller and the nip rollers isfabricated as the edge rollers and since there are no mechanisms such asclamp devices or pinch rolls protruding near the surface of a recordingmedium on which image read-out is conducted, it becomes possible toposition a light source and a light guide member close to the recordingmedium as in the case where a suction box is used, and to improve thelight guiding efficiency. That is, the scanning apparatus of the presentinvention has the advantage that it is free from noise and vibration asin the case where clamping devices or pinch rolls are used, and theadvantage that the scanning read-out system can be positioned close tothe recording medium as in the case where a suction box is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing an embodiment of the apparatus forscanning a sheet-shaped recording medium in accordance with the presentinvention when the apparatus is used for image read-out and a recordingmedium is introduced into the image read-out section,

FIG. 2 is a side view showing the embodiment of FIG. 1 when an imagestored in the recording medium is read out, and

FIG. 3 is a perspective view showing the embodiment in the condition ofFIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinbelow be described in further detailwith reference to the accompanying drawings.

FIGS. 1, 2 and 3 schematically show an embodiment of the apparatus forscanning a sheet-shaped recording medium in accordance with the presentinvention, which is used for reading out a radiation image. FIG. 1 showsthe step of introducing a stimulable phosphor sheet 6 carrying aradiation image stored therein into an image read-out section. FIG. 2shows the step of reading out the radiation image stored in thestimulable phosphor sheet 6, and FIG. 3 is a perspective view of theembodiment in the condition of FIG. 2.

Conveying rollers 3a and 3b and small nip rollers 5a, 5b, and 5c arepositioned between an inlet guide plate 1 and an outlet guide plate 2.The conveying rollers 3a and 3b are fabricated as a pair of edge rollersrotated by a precision motor (not shown) at a predetermined speed in thedirection as indicated by the arrow A. The nip rollers 5a, 5b, and 5care urged by resilient members 4a, 4b, and 4c onto the surfaces of theconveying rollers 3a and 3b.

The widths of the inlet guide plate 1 and the outlet guide plate 2 arelarger than the width of the stimulable phosphor sheet 6. The inletguide plate 1 and the outlet guide plate 2 are positioned approximatelysymmetrically with respect to the conveying rollers 3a and 3b.

The stimulable phosphor sheet 6 carrying a radiation image storedtherein is conveyed onto the inlet guide plate 1 as shown in FIG. 1. Thestimulable phosphor sheet 6 is then nipped between the conveying rollers3a and 3b and the nip rollers 5a, 5b, and 5c as the conveying rollers 3aand 3b are rotated, and is conveyed toward the outlet guide plate 2 asshown in FIG. 2. At this time, the stimulable phosphor sheet 6 is nippedin close contact with the surfaces of the conveying rollers 3a and 3b bythe nip rollers 5a, 5b, and 5c urged by the resilient members 4a, 4b,and 4c onto the surfaces of the conveying rollers 3a and 3b.

Thereafter, the stimulable phosphor sheet 6 is conveyed onto the outletguide plate 2.

As shown in FIG. 3, a light source 7 for emitting a light beam 9 and agalvanometer mirror 8 for making the light beam 9 impinge upon thestimulable phosphor sheet 6 so as to scan it forward and backward in thewidth direction thereof, i.e. in the main scanning direction arepositioned above the conveying rollers 3a and 3b. Further, between theconveying rollers 3a and 3b is positioned a light guide member 10 forguiding light emitted by the stimulable phosphor sheet 6 when thestimulable phosphor sheet 6 is exposed to the light beam 9 is positionedso that a front end face of the light guide member 10 extends in thewidth direction of the bent portion of the stimulable phosphor sheet 6.A rear end face of the light guide member 10 is closely contacted with aphotomultiplier 11 for converting the light emitted by the stimulablephosphor sheet 6 into an electric signal. The photomultiplier 11 isconnected to a cable 12 for sending the electric signal to an imagereproducing apparatus (not shown) for reproducing a visible image in aphotosensitive material or for displaying it on a cathode ray tube orthe like.

When the stimulable phosphor sheet 6 is exposed to the light beam 9 andthe light emitted thereby is detected, the stimulable phosphor sheet 6nipped between the conveying rollers 3a and 3b and the nip rollers 5a,5b, and 5c is bent and securely supported to fit the circumferentialsurfaces of the conveying rollers 3a and 3b. Therefore, the bent portionof the stimulable phosphor sheet 6 is freed from curling, distortion, orthe like by the bending action, and becomes even and straight in thewidth direction of the stimulable phosphor sheet 6. The bent portionthus made even and straight is scanned by the light beam 9 emitted bythe light source 7 via the galvanometer mirror 8 in the main scanningdirection, and is caused thereby to emit light in proportion to theradiation energy stored. During this step, the stimulable phosphor sheet6 is conveyed by the conveying rollers 3a and 3b and the nip rollers 5a,5b, and 5c at a predetermined speed toward the outlet guide plate 2,i.e. in the sub-scanning direction. Therefore, the whole surface of thestimulable phosphor sheet 6 is scanned by the light beam 9 in the mainscanning direction and in the sub-scanning direction.

It should be understood that the present invention can be embodied invarious types other than the above described embodiment. For example,the scanning apparatus in accordance with the present invention can, ofcourse, be applied also to an image recording apparatus. Further,instead of fabricating the conveying roller as the edge rollers, it isalso possible to fabricate at least one of the nip rollers as the edgerollers.

We claim:
 1. An apparatus for scanning a sheet-shaped stimulablephosphor recording medium, the apparatus comprising:(i) a conveyancemeans comprising a conveying roller and a plurality of nip rollers forforming nips for conveying said sheet-shaped stimulable phospharrecording medium in co-operation with said conveying roller bycontacting the surface of said conveying roller, and (ii) a scanningoptical system for scanning said sheet-shaped stimulable phosphorrecording medium, which is conveyed by said conveyance means, by a lightbeam in a scanning direction approximately normal to the conveyancedirection of said sheet-shaped stimulable phosphor recording medium,(iii) one of said conveying roller and said nip rollers being fabricatedas edge rollers contacting the other of said conveying roller and saidnip rollers only near both end portions of the other, (iv) said scanningoptical system being positioned on the side of said edge rollers forscanning between said edge rollers.
 2. An apparatus as defined in claim1 wherein said scanning optical system comprises a light guide memberand a photomultiplier for detecting the light emitted by saidsheet-shaped stimulable phosphor recording medium when said sheet shapedstimulable phosphor recording medium is scanned by the light beam.